getGadgetUri

Returns the gadget URI to be used for this portlet. Should be a relative URI pointing to the gadget replacing
this portlet. For example: 'rest/gadgets/1.0/g/com.atlassian.jira.gadgets/gadgets/filter-results-gadget.xml'

convertUserPrefs

Converts the propertySet in use by this portletConfiguration to a Map. Please note that multi
value values (values separated by _*|*_ in the propertyset) should be converted to values simply separated by
'|'. If '|' occurs in a value it needs to be % encoded to '%7C'.

Implementations may choose to convert properties to userprefs depending on the new gadgets requirements. This
doesn't have to represent a 1 to 1 mapping.